1. Field of the Invention:
This invention relates to image deflecting devices and, more particularly, optical devices for stabilizing an image against unexpected vibrations.
2. Description of the Related Art:
When the photographer takes shots from a running car, flying aircraft or another moving vehicle, vibrations are applied to a photographic system, causing production of an image blur. Even if the photographer is not riding on the moving vehicle, hand shakes will cause the image to blur. In either case, the image quality is dropped.
As disclosed, for example, in Japanese Patent Publications Nos. Sho 56-34847 and 57-7416, there is a technique of preventing the image from blurring by utilizing a prism of variable vertical angle which is added to the photographic lens. However, there are drawbacks that the size of the whole optical system including the prism is increased and when the vertical angle of the prism is made variable, a control mechanism for the vertical angle becomes complicated, etc. Also, meanwhile, as a proposal for removing these drawbacks, there is, for example, Japanese Laid-Open Patent Application No. Sho 62-47012. According to this proposal, a portion of the photographic lens system, i.e., a compensation lens unit, is made to decenter out of alignment to the optical axis. Thus, the image is deflected. Therefore, without a supplemental optical system such as a prism, a stabilized image can be obtained in a relatively small-sized photographic lens system with ease.
However, in the optical system described in the above Japanese Laid-Open Patent Application No. Sho 62-47012, when stabilizing the image against vibrations, the compensation lens unit which lies behind the afocal optical system must be decentered in a direction exactly perpendicular to the optical axis. However, actually, the compensation lens unit shifts to no small extent in the direction of the optical axis.
Such a shift of the compensation lens unit in the direction of the optical axis results in defocusing of the image, thus giving rise to a new problem. Although it is possible to some extent to move the compensation lens unit accurately in the direction perpendicular to the optical axis for the purpose of avoiding this problem as far as possible, a complicated structure of the moving mechanism, an increase of the size and a high production cost are required.
As the art related to the present invention, there are U.S. patent applications Ser. Nos. 116,541 filed on Nov. 4, 1987 (now U.S. Pat. No. 4,844,602), Ser. No. 156,930 filed on Feb. 17, 1988 (now U.S. Pat. No. 4,907,868) and Ser. No. 261,231 filed on Oct. 24. 1988.